change materials default folder

I am in the process of setting up a new computer and when I do this I make various drive images as I install software. This said I have now lost a few of the new materials I have made because by default Brazil saves new materials to the C drive, so if I redo an image I lose any new materials that have been saved since the drive image was made.

I am sure there is a way to change this but looking around I have yet to find the proper place to make these changes and figured I was not the first to want to do this. Hopefully someone will have the answer and save me future grief.